The hallmark of enzymes from secondary metabolic pathways is the pairing of powerful reactivity with exquisite site selectivity. The application of these biocatalytic tools in organic synthesis, however, remains under-utilized due to limitations in substrate scope and scalability. Here we report the reactivity of a monooxygenase (PikC) from the pikromycin pathway is modified through computationally-guided protein and substrate engineering, and applied to the oxidation of unactivated methylene C-H bonds. Molecular dynamics and quantum mechanical calculations were employed to develop a predictive model for substrate scope, site selectivity, and stereoselectivity of PikC mediated C-H oxidation. A suite of menthol derivatives was screened computationally and evaluated through in vitro reactions where each substrate adhered to the predicted models for selectivity and conversion to product. This platform was also expanded beyond menthol-based substrates to the selective hydroxylation of a variety of substrate cores ranging from cyclic to fused bicyclic and bridged bicyclic compounds.
A supramolecular polymeric adhesive was prepared from non-viscous, non-polymeric materials by water−participant hydrogen bonds. Pt−pyridine coordination and water−crown ether hydrogen bonding combine to effect the supramolecular polymerization. The supramolecular polymeric adhesive displays strong, reversible adhesion to hydrophilic surfaces, a property that forecasts the application of hydrogen bonding in advanced supramolecular materials.
Triflimide
(HNTf2) is a commercially available and highly
versatile super Brønsted acid. Owing to its strong acidity as
well as good compatibility with organic solvents, it has been widely
employed as an exceptional catalyst, promoter, or additive in a wide
range of organic reactions. On many occasions, triflimide has been
demonstrated to outperform triflic acid (TfOH). The uniquely outstanding
performance of triflimide also benefits from the low nucleophilicity
and noncoordinating property of its conjugate base (Tf2N–). Therefore, it has been employed as a precursor
toward a variety of cationic metal complexes or organic intermediates
with enhanced reactivity or catalytic activity. In this Review, we
describe these features and applications of triflimide in organic
synthesis, including its synthesis, physical properties, and role
as catalyst or promoter in organic reactions. At the end of this Review,
another closely related reagent, triflidic acid (HCTf3),
is also briefly introduced.
A new organocatalytic transfer hydrogenation strategy for the asymmetric synthesis of 1,1-diarylethanes is described. Under mild conditions, a range of 1,1-diarylethanes substituted with an o-hydroxyphenyl or indole unit could be obtained with excellent efficiency and enantioselectivity. We also extended the protocol to an unprecedented asymmetric hydroarylation of 1,1-diarylalkenes with indoles for the synthesis of a range of highly enantioenriched 1,1,1-triarylethanes bearing acyclic all-carbon quaternary stereocenters. These diaryl- and triarylethanes exhibit impressive cytotoxicity against a number of human cancer cell lines. Preliminary mechanistic studies combined with DFT calculations provided important insight into the reaction mechanism.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.